1. Field of the Invention
The present invention relates to agricultural implements, and, more particularly, to lift mechanisms for agricultural tillage implements.
2. Description of the Related Art
Farmers utilize a wide variety of tillage implements to prepare soil for planting. Some such implements include two or more sections coupled together to perform multiple functions as they are pulled through fields by a tractor. For example, a field cultivator is capable of simultaneously tilling soil and leveling the tilled soil in preparation for planting. A field cultivator has a frame that carries a number of cultivator shanks with shovels at their lower ends for tilling the soil. The field cultivator converts compacted soil into a level seedbed with a consistent depth for providing proper conditions for planting of a crop. Grass or residual crop material disposed on top of the soil is also worked into the seedbed so that it does not interfere with a seeding implement subsequently passing through the seedbed.
Tillage implements prepare the soil by way of mechanical agitation of various types, such as digging, stirring, and overturning. Examples of which include ploughing (overturning with moldboards or chiseling with chisel shanks), rototilling, rolling with cultipackers or other rollers, harrowing, and cultivating with cultivator shanks. Tillage is often classified into two types, primary and secondary. There is no strict definition of these two types, perhaps a loose distinction between the two is that tillage that is deeper and more thorough is thought of as primary, and tillage that is shallower is thought of as secondary. Primary tillage such as plowing produces a larger subsurface difference and tends to produce a rough surface finish, whereas secondary tillage tends to produce a smoother surface finish, such as that required to make a good seedbed for many crops. Harrowing and rototilling often combine primary and secondary tillage into one operation.
Wheels are often integral with tillage implements and are used for both transportation of the implement on road and between fields, and for depth control of the tillage implements in the field. When the wheels are used for depth control, in other words for controlling the height of the tillage implement above the ground surface in operation, often main lift wheels are used to control the height of the implement. Gauge wheels are then used to control the front to back levelling of the tillage implement. Because tillage implements are generally too wide to travel on roads between fields, tillage implements may be operable to fold up into a folded transport configuration. In this case, portions or wings of the framework that carries the field working devices, such as cultivator shanks, are folded for transport and unfolded for use in the field. The prior art includes various arrangements of main lift wheels, gauge wheels, and mechanisms for actuating them.
However, such prior art main lift wheel and gauge wheel lift mechanisms typically provide front to back and side to side levelling control and adjustability using individual lift cylinders for each lift wheel and gauge wheel. This requires complicated and expensive hydraulic valves, circuitry, and controls. Further, operation and control of such prior art lift mechanisms is often cumbersome and time consuming, requiring extensive operator training and knowledge. Alternately, prior art lift mechanisms minimize the number of cylinders involved, but at the expense of front to back and side to side levelling control and adjustability.
What is needed in the art is a lift and gauge wheel lift mechanism that is simple, reliable, strong, and stable. What is further needed in the art is a lift and gauge wheel lift mechanism that makes minimal use of hydraulic valves, cylinders, and controls, yet provides for simple front to back and side to side levelling control and adjustability.